A study of molybdenum radiation from alcator A

Abstract

Radiation emitted by molybdenum impurity ions in the Alcator A tokamak has been investigated. A grazing incidence monochromator photometrically calibrated against synchrotron radiation was used to determine absolute brightnesses of emission lines and the role of molybdenum radiative losses in the plasma discharge power balance. At line average electron densities of 3 × 10 14 cm −3, molybdenum radiation from the central (0–3 cm) region was equal to ∼17% of the local ohmic heating power, implying radiation from molybdenum ions does not dominate the power loss from the central part of the plasma. The temporal behavior of molybdenum ions injected by the laser blow off technique at n e = 3 × 10 14 cm −3 indicated that the molybdenum ion confinement time was finite in conflict with neoclassical theory. At lower densities (1–2 × 10 14 cm −3) the radiation from intrinsic molybdenum increased faster than the electron density during the discharge, indicating a buildup of molybdenum ions in the plasma.